1. Field of the Invention
The invention relates broadly to an improved apparatus and process for cutting elongated material, such as filamentary tows, into predetermined lengths, such as staple fiber. More particularly, it relates to an improvement to the means for holding the plurality of knives that are used to cut staple fiber of mixed cut length, wherein some of the staple fiber has a length of less than 3/4 inches. The holding means includes a support post to reduce blade breakage and contamination of the cut staple fiber.
2. Prior Art
Polyester staple fiber of mixed cut length, wherein some of the staple fiber has a length of less than 3/4 inches, is old in the art. For example, see Canadian Pat. No. 1,137,368 which discloses such a product and process and apparatus for making it.
There is extensive prior art with regard to staple fiber cutters which apparatus includes (i) a plurality of blades; (ii) means for supporting and spacing the blades; (iii) means for continuously passing polyester continuous filamentary tow over the edges of the spaced blades; and (iv) means for applying pressure on the tow to force the tow against the edges of the blades, whereby the tow is cut into staple fiber and simultaneously forced through the blades and their supporting means. For example, see U.S. Pat. Nos. 3,485,120 (Keith); 3,915,042 (Laird 1); 4,006,277 (Laird 2); and 4,141,115 (Fourne et al) and the figures labelled Prior Art herein.
FIGS. 1-4 (Prior Art) of this application are essentially identical to FIGS. 1-4 of U.S. Pat. No. 3,485,120 (Keith), "Method and Apparatus for Cutting Elongated Material". With reference to these figures, U.S. Pat. No. 3,485,120 discloses an apparatus for cutting material such as filamentary tows (74) into predetermined lengths comprising (a) a cutting assembly (18) including a plurality of spaced apart knife (28) edges (3) secured to a mounting member (22) at equal radial distances from a point on said mounting member (22) thereby forming a reel (18), each of said radial distances in every instance being less than the distance from said point to the periphery of said mounting member (22); (b) said cutting assembly (18) having means adapted to receive successive wrappings of material to be cut (64) in contact with a plurality of said knife (28) edges (30) so that no relative movement occurs between said material and said knife (28) edges (30) longitudinally of said material; and (c) means for forcing said material between adjacent knife (28) edges (30) [presser or pressure roll (42)], thereby severing said material into lengths of controlled dimensions. The knife blades (28) are removably mounted or inserted in slots (26) in "connector lengths" (24), which provide support for the knife blades. A more detailed description will be found in U.S. Pat. No. 3,485,120, particularly columns 3 and 4.
In general with such staple fiber cutters, in order to cut tow into a multiple length distribution, the spacing between successive cutting surfaces may be incrementally increased and/or adjacent cutting surfaces may be oriented in a nonparallel orientation with respect to each other.
It is also known that the foregoing types of staple fiber cutter frequently pose problems when the product includes fiber having lengths less than 3/4 inch. Three copending patent applications are addressed to the problems associated with cutting polyester tow into uniform fiber length of 1/2 inch. In particular, see application Ser. No. 06/343,241, filed Jan. 27, 1982 (Stikeleather et al); application Ser. No. 06/343,242, also filed Jan. 27, 1982 (Glick); and application Ser. No. 472,560, filed Mar. 7, 1983 (McLaughlin).
In addition, there has been public use for more than one year of cutters similar to those shown in FIGS. 1-4 (Prior Art), except that the knives (28) have been nonuniformly spaced in order to make mixed cut polyester staple fiber having length distributions shown in Canadian Pat. No. 1,137,368. However, asymmetrical support posts were not used (see Comparative Example 2 below).
In all the known prior art, each cutting blade has essentially been supported by support means that is completely symmetrical about the blade that is being supported. For example, FIG. 8 of U.S. Pat. No. 4,141,115 shows blades (44) supported by symmetrical slotted cylindrical rods (46).